Microcapsules and Microspheres formed from various natural and synthetic polymers and resins have become popular delivery vehicles for various active agents such as drugs, diagnostic reagents and the like. Degradable microcapsules and microspheres are of particular interest for use in so called "depot" formulations, where delivery of the active agent over an extended period of time is desired. Despite the growing number of uses of microcapsules and microspheres, there remains a need for an economic, safe and reliable method for their manufacture and formulation that avoids the most significant wastes and expenses associated with existing methods, while simultaneously enabling the ability to aseptically formulate the products in a simple and efficient manner.
Processes for preparing microcapsules and microspheres typically involve the formation of at least one dispersed phase in a continuous phase. The dispersed phase typically includes the active agent. In the case of microspheres, the dispersed phase will also typically include polymer so that, upon solidification in the continuous phase, the dispersed phase becomes a microsphere. Microcapsules are similarly formed using multiple phases. In a typical practice, a water-oil-water (w/o/w) emulsion is formed, and the polymer caused to precipitate out of one phase onto the surface of a dispersed phase to form a capsule wall thereon upon solidification of the polymer. Once the capsules or spheres are produced, they must then be formulated into a finished dosage form.
Most microsphere processes result in a suspension of particles in a suspending liquid that is not the suspending liquid desired for the final dosage form. Current techniques for processing and formulating microspheres and microcapsules into the final dosage form typically involve dead end filtration and powder filling processes. Although the powder processes can be made aseptic, they tend to have the drawbacks of using large volumes of flammable solvents, capital intensive equipment trains are generally required for a fixed scale and they take a comparatively long time to produce a finished batch. Likewise, the time and capital expense associated with powder filling processes can put one at a significant competitive disadvantage.
There is a need for a process that can efficiently, economically and aseptically process and formulate microcapsules and microspheres into final dosage forms.